function foo() {
	var x = 1;
	return function() {
		x += 1;
		console.log('x=' + x);
	}
}


var fun = foo(); // foo 已经返回
fun(); // fun 函数可以访问到foo 函数到变量 x
// closure = function which can access other functionA, even functionA is return (execute finished)
fun();